The invention generally relates to the field medical forceps.
A medical forceps is used in particular in the area of minimally invasive surgery for operations on a human or animal body. Without restricting generality, the medical forceps as provided by the present invention may be formed as grasping forceps for grasping tissue or as preparing forceps for cutting or preparing tissue.
A medical forceps known from the document DE 38 02 651 C2 has a handle which has a movable grip part and an immovable grip part. The movable grip part is fastened in a recess of an immovable housing part of the handle in such a way that it can pivot about a fixed pivot axis, which is arranged at the end of the movable grip part remote from the handle, which immovable housing part is for its part connected in one piece to the immovable grip part. The immovable grip part and the movable grip part project essentially transversely in relation to the longitudinal axis of the shaft of this forceps and form a scissors-grip-like arrangement. Running in the shaft in the direction of the longitudinal axis of the shaft is a force transmission element, which is movable axially in the direction of the longitudinal axis of the shaft. The force transmission element, which takes the form of a thin rod, serves for the force transmission from the movable grip part to the movable tool, for example a jaw part, at the distal end of the shaft. Correspondingly, the force transmission element is in operative connection with the movable tool on the one hand and the movable grip part on the other hand. With respect to the movable grip part, this operative connection is established by means of an articulated intermediate piece, which for its part is fastened pivotably about a fixed pivot axis in the recess of the housing part, and with which the force transmission element is articulated at an articulation point at a distance from the aforementioned fixed pivot axis. The articulated intermediate piece is connected in an articulated manner to the movable grip part by means of a pin, which engages in a slot which is arranged on the movable grip part at a distance from its fixed pivot axis.
In practical use of this medical forceps, it has been found that, in spite of observance of the smallest tolerances and the most careful production, the action of the force transmission from the movable grip part to the movable tool is not free from play. This has the disadvantage that the movable tool does not exactly follow the movements of the movable grip part. A further disadvantage of this known medical forceps is that the articulation point of the axially movable force transmission element on the articulated intermediate piece undergoes a circular movement when the movable grip part is actuated, which causes an additional movement of the force transmission element transversely in relation to the longitudinal direction of the shaft. This is one reason why this type of force transmission mechanism does not operate completely free from play.
A medical forceps which is designed in a particularly simple way with regard to the force transmission mechanism from the movable grip part to the movable tool is known from the document DE 32 15 949 A1.
In the case of this known medical forceps, the movable grip part is fastened on the immovable grip part in such a way that it can pivot about a fixed pivot axis and has a continuation which, as seen from the end of the movable grip part on the handle side, protrudes beyond the pivot axis and on which the force transmission element is directly articulated. Since this continuation undergoes a circular movement when the movable grip part pivots, here too there is once again the disadvantage that the axially movable force transmission element undergoes a circular movement.
Finally, the document DE-B 1 055 751 discloses a handle for surgical instruments which has a fixed grip part and a movable grip part, which as a difference from the two aforementioned known medical forceps run essentially in axial extension of the shaft and form a gripping arrangement which resembles a forceps grip. The movable grip part is connected by a connecting pin in an articulated manner directly to a slide, which is axially movable in the longitudinal direction of the force transmission element. The slide receives the instrument attachment. As the articulated connection of the movable grip part to the immovable grip part, arranged between the two is a leaf spring, which serves as a lever arm between the immovable grip part and the fixed grip part. The direct articulation of the movable grip part on the slide has the effect that the latter likewise does not undergo a strictly linear movement, because the articulation point of the movable grip part on the slide follows an arcuate movement curve as a result of the interposing of the leaf spring. This has as a consequence the disadvantage that the travel of the slide has to be restricted to a small range, in order to limit the circular movement of the articulation point of the movable grip part on the slide to small angles. Consequently, this force transmission mechanism is also not free from play. A further disadvantage of this force transmission mechanism is that it is only suitable for grip part arrangements in which the grip parts are arranged essentially in rectilinear extension of the shaft.